Epidemiology and Infection

Salivary diagnosis of rubella: a study of notified cases in the United Kingdom, 1991–4

M. E. RAMSAY a1, R. BRUGHA a1, D. W. G. BROWN a2, B. J. COHEN a2c1 and E. MILLER a1
a1 Immunisation Division, Communicable Disease Surveillance Centre
a2 Enteric and Respiratory Virus Laboratory, Central Public Health Laboratory, Colindale Avenue, London NW9 5HT, UK


Rubella infections, notified by general practitioners on the basis of a clinical diagnosis, were investigated by testing blood and saliva samples for specific IgM. Overall 52 (29%) of 178 cases with appropriately timed blood specimens were confirmed as recent rubella by IgM serology. Only 2 (3%) of 74 cases in children under 5 years were confirmed compared to 50 (48%) of 104 cases in older children and adults. The confirmation rate was lower (6 %) in those with documented vaccination history than in those without (42%). The specificity of saliva rubella IgM testing compared to testing corresponding blood samples was 99%. The overall sensitivity of saliva rubella IgM testing was 81%. This rose to 90% if results from inappropriately timed specimens and specimens taking more than 1 week to reach the laboratory were excluded. A corresponding saliva rubella IgG test was 98% sensitive and 100% specific. Of 126 rubella IgM negative cases, 25 (20%) were positive for parvovirus B19 IgM. This study confirmed that rubella surveillance based on clinical reports is not specific. It also demonstrated that saliva samples, if taken 7–42 days after onset of illness and transported rapidly to the laboratory, are a feasible alternative to blood samples for rubella surveillance.

(Accepted November 26 1997)

c1 Author for correspondence.